Silver (Ag) and water

Silver occurs in natural waters at low concentrations, usually as dissolved silver ions, complexes or particles associated with sediments. Mining, metal processing, wastewater and silver-containing products can raise local concentrations. The form of silver strongly affects its mobility, toxicity and removal.

Silver chemistry and sources

Silver can enter water through weathering of mineral deposits and through discharges from mining, refining, photography, electronics and other uses. Silver used in antimicrobial products and some point-of-use treatment devices can also be released. In water, silver may bind to chloride, sulfide, organic matter and suspended particles; therefore, total silver and dissolved silver can give different results.

Environmental and health considerations

Silver can be toxic to aquatic organisms at concentrations that depend on water chemistry and exposure conditions. It is not an essential nutrient for humans. WHO has not established a formal health-based drinking-water guideline because silver usually occurs naturally at low levels and the evidence is insufficient for a guideline; WHO gives a provisional reference value of 0.1 mg/L for limited situations, particularly where silver is used in point-of-use devices. The U.S. EPA also lists 0.1 mg/L as a non-enforceable secondary standard. These values have different purposes and are not universal legal limits.^[1]^[2]

Silver removal from water

WHO reports that conventional coagulation, sedimentation and filtration, as well as lime softening, can remove ionic silver under suitable conditions. The actual performance depends on silver speciation, pH, dissolved organic matter and competing substances. Analyze both total and dissolved silver and test the source water before selecting a process. Silver-bearing sludge, spent media or concentrate should be managed as a residual stream rather than discharged untreated.^[1]

Last reviewed: 3 November 2026 by Lenntech.